Methods for manufacturing micropolarizers

ABSTRACT

A method of mass producing a micropolarizer including the steps exposing films of predetermined polarization states to electromagnetic radiation through masks of predetermined patterns, etching away exposed parts of each film and aligning and laminating the films to one another to provide a micropolarizer comprising alternating sets of microscopic polarizers with different polarization states.

RELATED CASES

This is a Continuation application of application Ser. No. 08/527,094,filed Sep. 12, 1995 now U.S. Pat. No. 5,844,717, entitled “Method AndSystem For Producing Micropolarization Panels For Use In MicropolarizingSpatially Multiplexed Images Of 3-D Objects During Stereoscopic DisplayProcesses (As Amended)”; which is a continuation of application Ser. No.07/536,419, filed Jun. 11, 1990, entitled “METHODS FOR MANUFACTURINGPOLARIZERS”, now U.S. Pat. No. 5,327,285, issued on Jul. 5, 1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of polarizers and the highthroughput mass manufacturing of a new class of polarizars calledmicropolarizers. Micropolarizers have been developed for use in spatialmultiplexing and demultiplexing image elements in a 3-D stereo imagingand display system.

2. Description of Related Art

This invention is related to my co-pending application Ser. No.07/536,190 entitled “A System For Producing 3-D Stereo Images” filed oneven date herewith incorporated herein by reference in its entirety,which introduces a fundamentally new optical element called amicropolarizer. The function of the micropolarizer is to spatiallymultiplex and spatially demultiplex image elements in the 3-D stereoimaging and displaying system of the aforementioned co-pendingapplication. As shown in FIG. 1, the micropolarizer (μPol) 1, 2 is aregular array of cells 3 each of which comprises a set of microscopicpolarizers with polarization states P1 and P2. The array has a period pwhich is the cell size and is also the pixel size of the imaging ordisplaying devices.

It is possible to turn unpolarized light into linearly polarized lightby one of three well known means: 1) Nicol prisms; 2) Brewster Angle(condition of total internal reflection in dielectric materials); and 3)Polaroid film. These are called linear polarizers. The Polaroids arespecial plastic films which are inexpensive and come in very largesheets. They are made of polyvinyl alcohol (PVA) sheets stretchedbetween 3 to 5 times their original length and treated withiodine/potassium iodide mixture to produce the dichroic effect. Thiseffect is responsible for heavily attenuating (absorbing) the electricfield components along the stretching direction while transmitting theperpendicular electric field components. Therefore, if P1 is along thestretching direction of the PVA sheets, it is not transmitted, where asonly P2 is transmitted, producing polarized light. By simply rotatingthe PVA sheet 90 degrees, P1 state will now be transmitted and P2 willbe absorbed.

The aforementioned three known means for producing polarized light havealways been used in situations where the polarizer elements have largeareas, in excess of 1 cm². However, for 3-D imaging with μPols using 35mm film, to preserve the high resolution, the μPol array period p may beas small as 10 micron. Therefore, there is no prior art anticipating theuse of or teaching how to mass produce μPols having such smalldimensions.

SUMMARY OF THE INVENTION

The present invention provides a means for high through put massmanufacturing of micropolarizer arrays. To use the μPols in consumer 3-Dphotography, and printing applications, the economics dictate that thecost of μPols be in the range of 1 to 5 cents per square inch. For thisreason, the low cost PVA is the basis for the manufacturing process.

The present invention also provides a flexible μPols manufacturingprocess which can be adapted to low and high resolution situations aswell as alternative manufacturing methods, each of which may beadvantageous in certain applications and adaptable to processingdifferent polarizer materials. The present invention further provides anelectronically controllable μPol.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a micropolarizer array according to thepresent invention.

FIGS. 2 and 3 illustrate fabrication processes of linear micropolarizersusing, respectively, bleaching and selective application of iodine.

FIG. 4 shows final alignment and lamination processes for making linearmicropolarizers.

FIG. 5 illustrates a process for fabricating linear micropolarizers bymeans of etching.

FIG. 6 illustrates a method for patterning micropolarizer by mechanicalmeans.

FIG. 7 shows final alignment and lamination processes for making linearmicropolarizers by the etching method.

FIG. 8 shows final alignment and lam ion processes for making circularmicropolarizers by the etching method.

FIGS. 9 and 10 illustrate processes for making linear and circularpolarizers eliminating an alignment step.

FIGS. 11 and 12 illustrate photo-lithographic patterning steps.

FIG. 13 illustrates an automated high through-put process for continuousproduction of micropolarizer sheets by photo-lithographic means.

FIG. 14 illustrates an automated high through-put process for continuousproduction of micropolarizer sheets by direct application of bleachingink or iodine-based ink.

FIG. 15 illustrates an active electronically controllable micropolarizerbased on electro-optical effect of liquid crystals.

DETAILED DESCRIPTION

Since its invention by E. Land in the 1930's, polyvinyl alcohol (PVA)has been the polarizer material of choice. It is available from severalmanufacturers including the Polaroid Corporation. It comes as rolls 19inches wide and thousands of feet long. The PVA, which is 10 to 20micron thick, is stretched 2 to 5 times original length and treated withiodine to give it its dichroic (polarizing) property. The PVA treated inthis manner crystallizes and becomes brittle. The processes below employcertain chemical properties of the PVA. These are: i) resistance toorganic solvents and oils; ii) water solubility, 30% water and 70% ethylalcohol; iii) bleaching of the dichroic effect in hot humid atmosphereand by means of caustic solutions; iv) manifestation of dichroic effectby painting the PVA in iodine/potassium iodide solution; and v) thestabilization of the dichroic effect in boric acid solution. Thestarting PVA material comes laminated to a clear plastic substrate whichprotects the brittle PVA and facilitates handling and processing. Thesubstrate is made either of cellulose aceto bytyrate (CAB) or cellulosetriacetate (CTA), and is typically 50 to 125 micron thick. CAB and CTAare ultra-clear plastics and at the same time they are good barriersagainst humidity. For some applications, large glass plates are alsoused as substrates. Although other polymers, when stretched and treatedby dichroic dyes, exhibit similar optical activity to that of PVA andmay be fabricated into micropolarizers following the methods taughthere, only PVA is considered in the manufacturing processes described inthe present invention.

The physical principles on which the polarization of light and otherelectromagnetic waves, and the optical activity which produces phaseretardation (quarter wave and half wave retarders) are described inbooks on optics, such as: M. Born and E. Wolf, Principles of Optics,Pergamon Press, London, fourth edition, 1970; F. S. Crawford, Jr.,Waves, McGraw-Hill, New York, 1968; and M. V. Klein, Optics, Wiley, N.Y., 1970. There are several important facts used in this invention:

1. Two linear polarizers with their optical axis 90 degrees from eachother extinguish light.

2. A linear polarization which is 45 degrees from the optical axis of aquarter wave retarder is converted into a circular polarization.

3. A linear polarization which is 45 degrees from the optical axis of ahalf wave retarder is converted into a linear polarization rotated 90degrees.

4. Two linear polarization states, P1 and P2, 90 degrees from eachother, are converted into clockwise and counter-clockwise circularpolarization states by means of a quarter waver retarder.

5. A circular polarization is converted into a linear polarization bymeans of a linear polarizer.

6. A clockwise circular polarization is converted into acounter-clockwise polarization by means of a half-wave retarder.

The process for producing the micropolarizers, μPols, 1, 2 in FIG. 1 isdescribed in FIG. 2 which starts with a sheet of linear polarizer 5laminated onto a clear substrate 4. The laminate is coated withphotosensitive material 6 called photoresist. This can be one of severalwell known liquid photoresists marketed by Eastman Kodak and Shipley, orin the form of a dry photoresist sheet called Riston from the Du PontCompany. The latter is preferred because complete laminated rolls of thethree materials 3, 5, 6 can be produced and used to start the μPolsprocess. The photoresist is subsequently exposed and developed using amask having the desired pattern of the μPols cell 3 producing a patternwith polarization parts protected with the photoresist 6 and unprotectedparts 7 exposed for further treatment. These exposed parts 7 are treatedfor several seconds with a caustic solution e.g., a solution ofpotassium hydroxide. This bleaching solution removes the dichroic effectfrom the PVA so that the exposed parts 8 are no longer able to polarizelight. The photoresist is removed by known strippers, which have nobleaching effect, thus the first part 9 of the μPols fabrication isproduced. Alternatively, FIG. 3 shows a method for making linear μPolsby starting with a laminate of PVA 10 which is stretched but does notyet have the dichroic effect, i.e., it has not yet been treated withiodine, and the substrate 4. Following identical steps as above, windows7 are opened in the photoresist revealing part of the PVA. The next stepis to treat the exposed parts with a solution of iodine/potassium iodideand subsequently with a boric acid stabilizing solution. The exposedparts 11 of the PVA become polarizers while those protected with thephotoresist remain unpolarizers. Stripping the photoresist completes thefirst part of the process.

As illustrated in FIG. 4, a complete μPol is made using two parts 13, 14produced by either the process of FIG. 2 or FIG. 3 except that part 13has polarization axis oriented 90 degrees from that of part 14. The twoparts are aligned 15 so that the patterned polarizer areas do not overlap, and then laminated together to from the final product 16. The μPol16 is laminated with the PVA surfaces facing and in contact with eachother. The μPol 17 is laminated with the PVA of part 13 is in contactwith the substrate of part 14. The μPol 18 is laminated with thesubstrates of both parts are in contact with each other. Finally, it ispossible to produce the μPol 19 with only one substrate onto which twoPVA films are laminated and patterned according to the process describedabove. The above process leaves the patterned PVA film in place andachieves the desired result by either bleaching it or treating it withiodine solution. The processes described in FIGS. 5 and 6 achieve thedesired result by the complete removal of parts of the PVA. In FIG. 5,the starting material is any PVA film 20 (linear polarizer, quarter waveretarder, or half wave retarder) or any non-PVA optically activematerial laminated to a substrate. As described above, windows 7 in thephotoresist are opened. The exposed PVA 7 is removed 21 by means ofchemical etching (30% water/70% ethyl alcohol solution), photochemicaletching, eximer laser etching or reactive ion etching. Stripping thephotoresist, the first part 22 of the μPols process is completed.

The removal of PVA can also be accomplished by mechanical cutting ormilling means. FIG. 6 illustrates the process which uses a diamondcutter 66 mounted on a motor driven shaft 74. In one embodiment, the PVA68 is sandwiched between two polymers, such as poly-methyl methacrylate,PMMA, film 67, and the sandwich is laminated onto a substrate 69. Thediamond saw is used to cut channels. The channel width and the distancebetween the channels are identical. The PMMA serves to protect the topPVA surface from abrasion and protects the substrate from being cut bythe saw. Next the PMMA on top of the PVA and in the channel is dissolvedaway, leaving the part 71 with clean substrate surface 70. This part canbe used as is to complete the μPol fabrication or the original substrate69 is removed by dissolving away the rest of the PMMA, after havingattached a second substrate 72. This part which consists of thepatterned PVA 68 laminated to the substrate 72 is used in a subsequentstep to complete the μPol.

Even though this process is mechanical in nature, it has been shown inElectronic Business, May 14, 1990, page 125, that channels and spacingsas small as 5 micron can be made using diamond discs manufactured byDisco HI-TEC America Inc., of Santa Clara, Calif. Realizing that usingonly one disc makes the process slow and costly, the arrangement in FIG.6 is used where many discs 73 in parallel 75 is preferred. Each disc hasits center punched out in the shape of a hexagonal so that it can bemounted on a shaft 74 with a hexagonal cross section. Hundreds of suchdiscs are mounted on the same shaft and are spaced apart by means ofspacers 76 whose diameters are smaller than those of the discs. Thediameter difference is used to control the cutting depth. The spacersalso have hexagonal centers. The cutting discs and the spacers have thesame thickness in order to obtain identical channel width and channelspacing. The discs and spacers are mounted on the shaft tightly toprevent lateral motion, while the hexagonal shaft prevents slipping. Thediscs are made to rotate between 20,000 and 50,000 RPM and the laminateis cut in continuous fashion, thus achieving high through put.

To complete making a whole μPol the parts 22, 71, 72 prepared by the PVAremoval methods are used as in FIG. 7. If the PVA is a linear polarizer,then, parts 23, 24 have patterned polarizers which are oriented 90degrees from each other, and when aligned 25, and laminated together,complete linear μPols 26, 27, 28, 29 result. If the PVA is quarter waveretarder, then the parts 30, 31 of FIG. 8 have patterned retarders withoptical axes oriented 90 degrees from each other, and when aligned 32and laminated to a sheet of linear polarizer 33, complete circular μPols34, 35, 36 result.

Up until now all μPols have been made using two patterned parts alignedto each other and then laminated as in FIGS. 4, 7, and 8. It possiblemake μPols with a single patterned part 38 or 40 in FIGS. 9 and 10, andwithout the alignment step. In FIG. 9, the single patterned part 38consists of a patterned half-wave retarder on a substrate 4. It ismounted simply on a sheet of polarizer 39 with no alignment necessaryand a complete μPols results. If a linear polarizer sheet 39 is used,the result is a linear μPols. If a circular polarizer sheet 39 is used,the result is a circular μPols. In FIG. 10 the single patterned part 40has a linear polarizer which is simply mounted on a circular polarizersheet 41 to produce a complete μPols.

FIG. 11 shows the apparatus 42 used for contact printing of the laminate46 made of photoresist, PVA, and its substrate. The apparatus consistsof a vacuum box 47, and a vacuum pump 48 attached thereto. The top ofbox is flat surface with vacuum holes which hold the laminate flatduring exposure. The mask 45 with its emulsion facing down, makes directcontact with the photoresist surface with the aid of the top glass cover44. The very high intensity UV lamp 43 is then turned on for 30 to 60seconds to expose the photoresist. The laminate is subsequently removedfor development and the rest of the μPols fabrications processes asdescribed in FIGS. 2, 3, and 5. This printing process using apparatus 46is automated for large area μPols production as shown in FIG. 12. Thelaminate 46 is furnished in a large roll, is fed to apparatus 42 whenthe vacuum pump 48 is off and the mask and cover 44 are open. By meansof an electronic controller, the following automatic sequences arecarried out: (1) the vacuum is turned on; (2) the cover and mask arelowered; (3) the lamp is turned on for certain period of time; (4) thelamp is turned off; (5) the mask and cover are, lifted; (6) the vacuumis turned off; and (7) the laminate is advanced.

These steps are repeated until the whole roll is finished. The exposedroll 49 is then processed further. This exposure apparatus is simple andhas no critical alignment requirements.

The fully automated embodiment in FIG. 13 is used for continuous massproduction. The raw roll of laminate 46 enters from the right and thefinished roll 56 of μPols exists from the left. As one laminate segmentis exposed, it is advanced to the left, developed and rinsed in station50. Said segment is then further advanced to the left to be dried instation 51, and advanced further to section 52. This station carries outthe most critical μPols process by one of three methods discussed abovein connection with FIGS. 2, 3, and 5. These are:

1. Bleaching by means of potassium hydroxide then rinsing.

2. Polarizing by means of iodine/potassium iodide solution, boric acidstabilizing solution, then water/methyl alcohol rinse.

3. Dry or wet etching of the PVA.

After the rinsing step in station 52, the segment is advanced to station53 for drying and heat treatment. The photoresist stripping and rinsingis done in 54 and the final drying step in 55. The finished roll 56 islaminated with a polarizer sheet according to FIGS. 9 and 10 completethe μPols.

The photolithographic printing used above involves several steps:

1. Application of the photoresist

2. Baking

3. Making contact with the mask

4. Exposure

5. Development

6. Rinsing

7. Drying

8. Post baking

9. Stripping

10. Rinsing

11. Drying

These steps have been eliminated by using the mechanical methoddescribed in FIG. 6. They are also completely eliminated by using theembodiment illustrated in FIG. 14. This apparatus 57 promises to be theleast expensive high volume manufacturing process for μPols. It consistsof a plate drum 58 to which a plate a fixed, a blanket drum 59 which hasa rubber surface, and an impression drum 60. The inks from ink fountains62, 65, are transferred to the plate by means of rollers 63, 64. Thepattern is transferred from the plate to the blanket drum which in turnit transfers to the PVA laminate 61. The rotation of the blanket drumand the impression drums draws in the laminate, and blanket rubbersurface pressing on the laminate causes proper printing. Although thehardware is similar to that used in offset printing press, the processis different from offset printing. The principal difference is in theink formulation. In offset printing slightly acidic water is used infountain 65, and an oil-based paint (linseed oil, pigments, binder, andother additives) is used in fountain 62. These are not intended tointeract w the paper. The pigments in the oil based solution will remainbonded to the paper, and the water evaporates. In the μPols printingprocess, on the other hand, the oil based solution is clear and is notintended to remain, while the water based solution is intended tointeract with the PVA and permanently modify it, by bleaching it or byendowing it with the dichroic property. Another difference is the use ofthe negative image on the plate to print a positive image of the patternon the PVA laminate, whereas in the offset printing, the oppositeoccurs. The plates are made by means which are well known in the offsetprinting industry.

The μPols process using apparatus 57 has three embodiments which dependon the content of the water based solutions in fountain 65, whilefountain 62 contains a fast drying clear oil solution:

1. Selective Bleaching: The water based solution contains a bleachingagent such as potassium hydroxide or sodium hydroxide which appliedselectively as pattern on the polarized PVA. Where applied, the solutionremoves the iodine and its polarizing effect. Rinsing and drying stepsfollow this bleaching step.

2. Selective Dichroism: The water based solution contains aiodine/potassium iodide which is applied selectively as a pattern on theunpolarized PVA. Where applied, the solution turns the PVA into apolarizer. This step is followed by a stabilizing step using a boricacid solution and subsequently rinsing using a methyl alcohol solutionand drying steps.

3. Selective Etching: The water based solution contains a clear polymerwhich is applied selectively as a pattern on the polarized orunpolarized PVA. Where applied, the solution leaves a protective polymerlayer. This step is followed by an etching step to remove theunprotected PVA, by rinsing and drying steps.

Electrically Controllable Micropolarizers

There are applications in which a variable μPols are needed, and inparticular, μPols which are electronically alterable. This can beaccomplished by using electro-optical materials such as liquid crystalsor organic nonlinear optical polymers, see C. C. Teng and H. T. Man,Applied Physics Letters, 30, 1734 (1990), or magneto-optical materialswhich have large Faraday rotation. All these materials rotate thepolarization of incident radiations by applying voltages or magneticfields. The preferred embodiment 77 in FIG. 15 uses a twisted nematicliquid crystal 78 which rotates the polarization 90 degrees by applyinga voltage alternating at 10 to 20 KHz and having an RMS value of about10 volts. This voltage is applied between the checker-board patternedtransparent electrode made of indium-tin oxide ITO 82 on a glasssubstrate 80 and an unpatterned ground ITO layer 81 deposited on asecond glass substrate 79. The patterned ITO 82 are connected to acommon voltage bus 85. Each connection 86 is made of aluminum film whosearea is a small percentage of the ITO area, in the order of 10%. Thus wecreated two types of cells: One type which has liquid crystal and ITO81, 82 on both sides, will be affected by the applied electric field;and the other type which has liquid crystal but has ITO 81 on one sideonly and hence will not be affected by the applied electric field. Thepolarizer sheet 83 with polarization state P1 is laminated to the glasssubstrate 80 completes the electronic μPols.

The operating principles of electronically switchable μPols is asfollows: When the voltage 84 is zero, the polarization P1 of theincident light will not change. When a voltage is applied, the cellswith ITO on both sides will rotate the polarization to a state P2, whilethe cells with ITO on one side only leave the polarization P1 unchanged.The end result is a regular periodic array of cells with twopolarization states P1 and P2. This is a μPol that can be turned off andon.

What is claimed is:
 1. A system for fabricating a micropolarizationpanel for use in stereoscopic viewing a 3-D object recorded in aspatially multiplexed image of said 3-D object, said system comprising:film providing apparatus for providing a supply of film materialcharacterized by an ability to either phase shift or polarize lightpassing therethrough; film coating apparatus for coating said filmmaterial with a protective mask having a predetermined pattern thatexposes preselected parts of said film material; and film treatingapparatus for treating said film material with said protective mask soas to permanently form first and second optically transparent patternstherein, wherein said first optically transparent pattern imparts afirst polarization state, P1, to light emanating from pixels throughsaid first optically transparent pattern, and said second opticallytransparent pattern imparts a second polarization state, P2, to lightemanating from pixels through said second optically transparent pattern,and wherein said first optically transparent pattern is a logicalinverse of said second optically transparent pattern; and film cuttingapparatus for cutting said treated film material so as to form amicropolarization panel for use in stereoscopic viewing of a 3-D objectrecorded in a spatially-multiplexed image of said 3-D object.
 2. Thesystem of claim 1, wherein said first and second polarization states arelinear polarization states which are oriented 90° from one another. 3.The system of claim 1, wherein said film treating apparatus comprisesapparatus for applying a caustic agent to said film coated with saidprotective mask.
 4. The system of claim 1, which further compriseslaminating apparatus for applying a lamination layer upon said treatedfilm material.
 5. The system of claim 1, wherein said film providingapparatus comprises first and second rotatable drums for supporting andtransporting said film material.
 6. A method for fabricating amicropolarization panel for use in stereoscopic viewing a 3-D objectrecorded in a spatially multiplexed image of said 3-D object, saidmethod comprising the steps of: (a) providing a sheet of wave retarderfilm material; (b) applying a protective coating to said wave retarderfilm material; and (c) chemically treating said wave retarder filmmaterial to selectively remove portions thereof to produce first andsecond optically transparent patterns in said sheet of wave retarderfilm material so as to provide a micropolarization panel for use instereoscopic viewing of a 3-D object recorded in a spatially-multiplexedimage of said 3-D object, wherein said first optically transparentpattern imparts a first polarization state P1 to light emanating throughsaid first optically transparent pattern, said second opticallytransparent pattern imparts a second polarization state P2 to lightemanating through said second optically transparent pattern, and saidsecond optically transparent pattern is the logical compliment patternof said first optically transparent pattern.
 7. The method of claim 6,wherein said sheet of wave retarder film is a sheet of half-waveretarder.
 8. A system for fabricating a patterned polarizer film,comprising: film providing apparatus for providing a film; film coatingapparatus for coating said film with a protective mask having apredetermined pattern that exposes preselected portions of said film;and film treating means for thereafter treating said film to affect thepreselected parts of said film to provide a pattern of polarized andunpolarized portions of said film, the polarized parts of the filmhaving a first polarization state, P1.
 9. The system of claim 8, whereinsaid film comprises a polarized film having the first polarizationstate, P1; and wherein said film treating apparatus comprisespolarization state removing apparatus for removing the polarizationstate of the preselected exposed portions of said film.
 10. The systemof claim 8, wherein said film comprises a polarized PVA film.
 11. Thesystem of claim 8, wherein said film comprises a cholesteric liquidcrystal polarizer.
 12. The system of claim 8, wherein said filmcomprises a half-wave retarder.
 13. The system of claim 8, wherein saidfilm comprises a quarter-wave retarder.
 14. The system of claim 8,wherein said polarization state removing apparatus comprises means forapplying an enchant or a solvent solution to the preselected exposedportions of said film.
 15. The system of claim 8, which furthercomprises film laminating apparatus for laminating said film to a sheetof polarizer.
 16. The system of claim 15, wherein the film is aretarder, and wherein the sheet of polarizer comprises a sheet of linearpolarizer material.
 17. The system of claim 8, wherein the filmcomprises a polarized film having the first polarization state, P1; andwherein said polarization state removing apparatus comprises means foretching away the preselected portions of said film to provide a patternof polarized portions of said film.
 18. A system for fabricatingmicropolarizing material for use in stereoscopic viewing a 3-D objectrecorded in a spatially multiplexed image of said 3-D object, saidsystem comprising: (a) apparatus for providing a film coated with aprotective mask having a predetermined pattern that exposes preselectedparts of the film; and (b) apparatus for treating said film to affectthe preselected parts of said film to provide micropolarization materialfor use in stereoscopic viewing of a 3-D object recorded in aspatially-multiplexed image of said 3-D object, having a pattern ofpolarized and unpolarized parts of the film, wherein the polarized partsof said film have a first polarization state, P1.
 19. A method offabricating a micropolarization panel for use in stereoscopic viewing a3-D object recorded in a spatially multiplexed image of said 3-D object,said system comprising the steps of: (a) providing a sheet of waveretarder film; (b) applying a protective coating to said wave retarderfilm; and (c) for chemically treating said wave retarder film toselectively remove portions thereof to produce first and secondoptically transparent patterns in said sheet of wave retarder film so asto provide a micropolarization panel for use in stereoscopic viewing ofa 3-D object recorded in a spatially-multiplexed image of said 3-Dobject, whereby said first optically transparent pattern imparts a firstpolarization state P1 to light emanating through said first opticallytransparent pattern, said second optically transparent pattern imparts asecond polarization state P2 to light emanating through said secondoptically transparent pattern, and said second optically transparentpattern is the logical compliment pattern of said first opticallytransparent pattern.